The field of the invention is the use of magainins and related peptides to selectively lyse malaria infected erythrocytes.
Intracellular pathogens comprise a particularly intractable source of pathogenic infections. Notorious clinical examples include Rickettsia, Chlamydia, Plasmodia species. Malaria-causing Plasmodia species in particular are the most devastating sources of infectious human morbidity and mortality on earth, with approximately 250 million to 500 million new cases each year, malaria is the direct cause of 1 million to 1.5 million deaths per year. By seeking refuge inside host cells, intracellular pathogens such as Plasmodia are able to evade many traditional host defenses. Instead, the host must resort to immune mechanisms capable of distinguishing infected from uninfected cells.
Magainins, PGLa and XPF comprise a class of linear, amphipathic cationic peptides originally found in the skin of Xenopus laevis and shown to have broad-spectrum antimicrobial activity. These peptides have been reported to exhibit cidal activity against many infectious agents including bacteria, fungi, protozoa and viruses. In particular, magainins have been reported to disrupt extracellular stages of Plasmodia parasites. Unfortunately, the life cycles of the Plasmodia, like many intracellular pathogens, comprise only brief extracellular stages and the magainins were reported to have no effect on their intracellular development.
Gwadz et al. (1989) Infection and Immunity 57, 2628-2633 report that magainins had no effect on the intracellular development of Plasmodium species.
Zasloff (1989) U.S. Pat. No. 4,810,777 discloses a class of antibiotic polypeptides termed magainins.
Zasloff(1996) U.S. Pat. No. 5,567,681 discloses a antibiotic properties of polypeptides termed PGLa and XPF.
Huang et al. (1990) Antimicrobial Agents and Chemotherapy 34, 1824-1826 report the effect of magainins against pathogenic protozoa.
Aboudy et al. (1994) Int. J. Peptide Protein Res. 43, 573-582 report the effect of magainins against herpes simplex virus types 1 and 2.
Jacob and Zasloff (1994) Antimicrobial Peptides. While, Chichester (Ciba Foundation Symposium 186), p197-223 review the potential therapuetic applications of magainins.
Matsuzaki et al. (1995) Biochemistry 34, 3432-3429, report on the molecular basis for membrane selectivity of magainin 2.
Matsuzaki et al. (1994) Biochemistry 34, 3342-3349, report on the structural orientation of magainin 2 in phospholipid bilayers.
Tytler et al. (1995) Biochemistry 34, 4395-4401, report on the molecular basis for prokaryotic specificity of magainin-induced lysis.
The invention provides methods and compositions for inhibiting the development of intracellular parasites by treating such cells with an effective concentration of a magainin, PGLa or XPF peptide under conditions whereby the development of the parasite in said cell is inhibited. The targeted parasites have been found to increase in the accessibility of the plasma membrane of the cell to the peptide and effect an increase in the cytopathic, especially lytic, sensitivity of the cell to the peptide.
In one application, the invention provides methods for treating infected blood comprising both infected erythrocytes having an intracellular parasite and uninfected erythrocytes, by contacting the blood with a magainin, PGLa or XPF peptide under conditions whereby the development of the parasite in the infected erythrocytes is inhibited and the infected erythrocytes evidence relatively increased cytopathology relative to the uninfected cells.
In preferred embodiments of the disclosed methods, the infected cell is a resident erythrocyte, the parasite is a Plasmodium species, the peptide is magainin 2 and the conditions comprise a localized concentration of the peptide of between 5 and 100 xcexcM.